[time-nuts] simulation of interconnected clocks

[Jim Lux]

On 11/30/13 5:33 PM, Hal Murray wrote:
>
> tvb at LeapSecond.com said:
>> Attached is frequency and ADEV of my heart beat for 10 hours.
>
> Neat.  What did you use to collect the raw data?
>
>

There's a few Arduino/Sparkfun/Adafruit widgets out there that receive 
the signals from off the shelf Polar heart rate monitors.

I had a grad student last summer build a box to log heart beats using 
photoplethysmography (photocell sensing blood flow in fingertip). He 
used a widget from one of the dealers that has the analog circuitry to 
buffer the optical sensor.

If I were collecting it on a long term (many hours) basis, I'd go with 
ECG based approaches (which is what the Polar sensors use), but with 
stick on electrodes. Motion artifacts are a big problem.

Holter is the big name in commercial ECG loggers, but they're real 
pricey (being FDA approved medical devices and all).

Microwave monitoring (radar) is a good "standoff" way to measure 
heartbeats, but only works in fixed locations (e.g. I can set it up in 
my office, in my car, or a room at home, and collect data, but it 
doesn't work well when you're out walking around).  If you get one of 
those microwave Doppler door sensors at 10.5 or 24 GHz, you can get a 
good heartbeat signal from them.